According to the Oniguruma documentation, the \d character type matches:
decimal digit char
Unicode: General_Category -- Decimal_Number
However, scanning for \d in a string with all the Decimal_Number characters results in only latin 0-9 digits being matched:
#encoding: utf-8
require 'open-uri'
html = open("http://www.fileformat.info/info/unicode/category/Nd/list.htm").read
digits = html.scan(/U\+([\da-f]{4})/i).flatten.map{ |s| s.to_i(16) }.pack('U*')
puts digits.encoding, digits
#=> UTF-8
#=> 0123456789٠١٢٣٤٥٦٧٨٩۰۱۲۳۴۵۶۷۸۹߀߁߂߃߄߅߆߇߈߉०१२३४५६७८९০১২৩৪৫৬৭৮৯੦੧੨…
p RUBY_DESCRIPTION, digits.scan(/\d/)
#=> "ruby 1.9.2p180 (2011-02-18) [i386-mingw32]"
#=> ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
Am I misreading the documentation? Why doesn't \d match other Unicode numerals, and/or is there a way to make it do so?